German and Peruvian archeologists work at the circular 5,500-year-old sunken ceremonial plaza, built of stones and adobe, part of the Sechin Bajo archaeological complex in Casma, Andes foothills, 330... (Associated Press)

(Newser)
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Archaeologists in Peru have unearthed one of the oldest structures in the Americas, Reuters reports. Carbon dating indicates the ceremonial plaza in Casma is 5,500 years old, scientists at the dig say. That's 500 years older than the nearby ancient citadel of Caral, previously thought be Peru’s oldest ruins. "It's an impressive find," said the project's supervisor.

"We think it's the oldest urban site found in the Americas," said an archaeologist who supervised the find. "We've found other pieces of architecture underneath the plaza that could be even older," added another. "There are four or five plazas deeper down, which means the structure was rebuilt several times, perhaps every 100 to 300 years."